1. Field of the Invention
The present invention relates to an exhaust chamber in the motorcycle exhaust system and, more particularly, to an exhaust chamber disposed on the motorcycle exhaust system at a location upstream of a muffler.
2. Description of the Related Art
The motorcycle exhaust system of a type having an exhaust control valve disposed at a location upstream of the muffler for adjusting the opening of the exhaust passage has been known. In this motorcycle exhaust system, it has been recognized that disposition of the exhaust control valve inside the muffler or the exhaust pipe is apt to impose a limitation on the freedom of design choice such as, for example, layout and/or material for the muffler or an exhaust pipe. To alleviate the limitation on the freedom of design choice, the Japanese Laid-open Patent Publication No. 2008-106644, first published May 8, 2008, discloses the use of an exhaust chamber, disposed upstream of the muffler and including communicating pipes communicated with a plurality of expansion compartments, and an exhaust control valve disposed within at least one of the communicating pipes for adjusting the sectional area of a passage inside such one of the communicating pipe.
However, according to the previously mentioned patent document, the exhaust control valve is disposed within the communicating passage inside the exhaust chamber, and, accordingly, the internal structure of the exhaust chamber tends to be complicated. In addition, the exhaust control valve employed require complicated maintenance and servicing works.